Since the campaign accelerated last week, Russian authorities have demanded registration and finance documents from dozens of NGOs across the country.

Investigators have visited major organizations such as Memorial, Human Rights Watch, and Amnesty International.

Human rights council member Pavel Chikov said the searches were possibly aimed at paralyzing and intimidating NGOs.

Chikov said that by his count, 100 or so organizations from 25 regions across Russia had reported inspections.

The head of the Moscow Helsinki Group, Lyudmila Alekseyeva, told RFE/RL that her organization was the latest to receive a visit by Russian authorities.

"Representatives of the Justice Ministry and the prosecutor's office came and demanded a rather limited set of documents," Alekseyeva said.

"We made photocopies of some of the documents immediately and handed them over and agreed that we would provide the remaining documents when they were ready. That was a rather limited set of documents, they didn't ask for any accounting documents."

The authorities say they are checking if the NGOs are in compliance with new laws on foreign financing.

'Foreign Agents'

Part of the new laws include requirements that NGOs operating in Russia be officially registered as "foreign agents" if they receive financing from abroad.

Russian President Vladimir Putin has described the ongoing inspections as "routine measures."

At a meeting with Russia's human rights ombudsman on March 28, Putin said the inspections were intended to determine whether the activities of the groups were "in compliance with their stated goals and with Russian legislation."

He also said law enforcement agencies should not be overzealous.

The European Union has called the searches "worrisome," while State Department spokeswoman Victoria Nuland said the United States had "shared its concerns" with the Russian government.

"The sheer scope of these inspections now, which are now, as I said, targeting not just NGOs who are subject to the changes under Russian law but also targeting civil organizations that are not subject to those laws, like religious organizations, educational organizations, really gives us concern that this is some kind of a witch hunt," Nuland said.

German officials have said the raids on German institutions in Russia could lead to a deterioration of ties between Moscow and Berlin.

With reporting by Interfax, AFP, Reuters, and RFE/RL's Russian Service